package Apache::AdBlocker;
# file: Apache/AdBlocker.pm

use strict;
use vars qw(@ISA $VERSION);
use Apache::Constants qw(:common);
use GD ();
use Image::Size qw(imgsize);
use LWP::UserAgent ();

@ISA = qw(LWP::UserAgent);
$VERSION = '1.00';

my $UA = __PACKAGE__->new;
$UA->agent(join "/", __PACKAGE__, $VERSION);

sub redirect_ok {0}

my $Ad = join "|", qw{ads? advertisements? banners? adv promotions?};

sub handler {
    my $r = shift;
    return DECLINED unless $r->proxyreq;
    $r->handler("perl-script"); #ok, let's do it
    $r->push_handlers(PerlHandler => \&proxy_handler);
    return OK;
}

sub proxy_handler {
    my $r = shift;
    
    my $request = HTTP::Request->new($r->method, $r->uri);
    
    $r->headers_in->do(sub { 
	$request->header(@_); 
    });

    # copy POST data, if any
    if($r->method eq 'POST') {
	my $len = $r->header_in('Content-length');
	my $buf;
	$r->read($buf, $len);
	$request->content($buf);
    }

    my $response = $UA->request($request);
    $r->content_type($response->header('Content-type'));

    #feed response back into our request_rec*
    $r->status($response->code);
    $r->status_line(join " ", $response->code, $response->message);
    $response->scan(sub {
	$r->header_out(@_);
    });

    if ($r->header_only) {
	$r->send_http_header();
	return OK;
    }

    my $content = \$response->content;
    if($r->content_type =~ /^image/ and $r->uri =~ /\b($Ad)\b/i) {
	block_ad($content);
	$r->content_type("image/gif");
    }

    $r->content_type('text/html') unless $$content;
    $r->send_http_header;
    $r->print($$content || $response->error_as_HTML);

    return OK;
}

sub block_ad {
    my $data = shift;
    my($x, $y) = imgsize($data);
    
    my $im = GD::Image->new($x,$y);
    
    my $white = $im->colorAllocate(255,255,255);
    my $black = $im->colorAllocate(0,0,0);       
    my $red = $im->colorAllocate(255,0,0);      
    
    $im->transparent($white);
    $im->string(GD::gdLargeFont(),5,5,"Blocked Ad",$red);
    $im->rectangle(0,0,$x-1,$y-1,$black);
    
    $$data = $im->gif;
}

1;
__END__